Methods are known for fixing an elastic element or member, such as an elastomeric band or ribbon, to a flexible, substantially inelastic web of material defining clothing or components therefor, including briefs, panty briefs, disposable diapers, and the like.
Methods are known for applying an elastic element to a continuously moving web. The U.S. Pat. No. 3,828,367 to Bourgeois discloses a method for securing a stretched elastic element to a non-elastic fabric web and maintaining the assembled element on the web in a stretched condition until cut transversely of the direction of travel to produce separated panels. The apparatus is disclosed as including a rotating cylinder with a curved guide for imparting a non-linear configuration to the elastic element so that the ribbon follows a predetermined contour on the non-elastic fabric.
The U.S. Pat. No. 4,081,301 to Buell cites other prior art patents showing ways in which an elastic ribbon is joined to a moving web of material. The Buell patent itself discloses a method and apparatus for continuously attaching discrete lengths of elastic ribbon to a moving web in which the elastic ribbon is fed in a stretched condition to the web and in which the elastic ribbon is intermittently secured to predetermined regions of the web while so stretched. Subsequently, the web and elastic ribbon are transversely cut in an area where the elastic ribbon is not secured to the web, thereby forming severed, unadhered portions of elastic at both ends of each discrete length of stretched elastic ribbon adhered to the web and allowing the severed, unadhered ends of the elastic ribbon to relax and contract to their unstretched state.
With the method disclosed in the above-discussed Buell patent, it is important that (1) the moving elastic ribbon be secured to the moving web precisely at the predetermined regions on the web and (2) the moving elastic ribbon and moving web be severed precisely in the region where the elastic ribbon is not adhered to the web. For example, if the stretched elastic ribbon were accidentally adhered beyond the predetermined region and were then severed where it was accidentally adhered, the elastic ribbon would contract to impart an elasticized character beyond the desired predetermined region.
Thus, the securing mechanisms (such as adhesive applicators, heat sealing devices, etc.) must be carefully controlled and actuated to effect securement precisely in the desired regions. With very high speed manufacturing operations, accurate control of such mechanisms becomes difficult. Further, if the securing mechanism is a movable device, stresses imparted to the moving securing mechanism increase owing to the more rapid accelerations and decelerations which necessarily occur in high speed operations.
Also, the severing mechanism for cutting the web and elastic ribbon must be carefully controlled so that the elastic ribbon is cut in the unattached region. Obviously, at high speed manufacturing conditions, proper registration of a cutting mechanism becomes more difficult. If the cutting mechanism is a movable device, it must be designed to accommodate the higher stresses which result from the increased accelerations and decelerations.
In order to avoid the problems of precisely and accurately registering ribbon-securing and ribbon-severing mechanisms in high speed operations and in order to avoid the imposition of high stresses on such mechanisms subjected to rapid and intermittent movement, it would be desirable to provide a method and apparatus in which an elastic member could be secured to the moving web with stretched portions and unstretched or relaxed portions already formed in the elastic member before securement to the web.
With such a method, the securing means is preferably operated along the entire length of the elastic member so as to avoid the problems associated with high speed cyclical operation. Further, with this method, severing of the member in the relaxed segment would not cause the web to be further contracted. This would be true whether or not the relaxed segment of the elastic member was secured to the web.